Optical communication networks have increasingly been seen as the solution to many bandwidth problems that occur fairly frequently on other networks. Optical communication networks use optical fibers, which are typically less susceptible to external noise than other media and are typically cheaper to make than copper wire. Furthermore, optical fibers provide greater bandwidth than copper wires, which results in higher data rates. Typically, data streams that are transferred through a communications system can be divided from each other according to several different protocols. In optics, the data streams are often separated by wavelength. Protocols that separate data based on wavelength are generally referred to as wavelength division multiplexing (WDM) protocols.
WDM in fiber optics is typically either dense wavelength division multiplexing (DWDM), or coarse wavelength division multiplexing (CWDM). CWDM has only recently been standardized by the International Telecommunications Union Standards Committee (ITU-T) as the G.694.2 CWDM channel grid. The deployment capability of CWDM systems is enhanced by the introduction of zero water-peak fibers (ZWPFs) (ITU-T G.652.C) such as the AllWave® fiber, a zero water peak fiber available from OFS Fitel of Norcross, Ga. ZWPFs remove most of the hydroxyl (OH) ions that remain in manufactured optical fiber. Hydroxyl ions are removed because of the fact that these hydroxyl ions resonate in several different modes. More particularly, the resonation of the hydroxyl ions causes an attenuation peak at about 1400 nm in the optical spectrum. Consequently, ZWPFs offer up to 33% more CWDM capacity than standard single mode fiber (SSMF).
CWDM systems operate as passive systems, with wide divisions between the wavelength channels used to transmit data. Thus, CWDM typically uses the entire available optical spectrum to transmit 16 channels of network traffic. These wavelengths range from about 1310 nm to about 1610 nm, with channels spaced 20 nm from each other. This wide channel spacing allows for less precision with respect to the lasers used for transmitting signals and less precision in the filtering devices used to filter adjacent channels.
In contrast, DWDM systems are active systems, typically transmitting on a variable number of channels with 1.6 nm, 0.8 nm or 0.4 nm spacing, depending upon the implementation. The narrow channel spacing requires very precise filters with high selectivity. Such highly selective filters increase the expense of the system. Moreover, the narrow channel spacing requires high precision, cooled lasers which exhibit low wavelength drift and dispersion characteristics, thereby also increasing the expense of the system. However, because of the active nature of the system, a signal may be transmitted farther along the fiber, thereby increasing the circumference of networks having a hubbed-ring configuration.
It would be desirable to increase the coverage area of CWDM systems to compete with DWDM systems, particularly in cost sensitive environments. Consequently, a need exists for a system and method that address these and/or other shortcomings of existing CWDM systems.